1. Field of the Invention
This invention relates to hair curlers for having hair tresses wound thereon in order to impart a curl to the hair. In particular, this invention relates to elongated flexible hair curlers.
2. Description of the Prior Art
Elongated flexible hair curlers have been known for quite some time. Such curlers generally comprise cylindrical bodies made of resilient material such as foam or sponge rubber and have a wire or soft metal core embedded within the body along the axis of the curler. An elongated flexible curler is much longer than an inflexible curler in order to enable it to be bent over on itself to retain a hair tress wound thereon. This avoids the necessity of a clip to hold the hair as is required with inflexible curlers. Elongated flexible curlers also may be bent in a variety of positions after hair is wound thereon and thus may impart a variety of waves to the hair. The metal core enables the curler to be bent and to retain the position it is placed in until it is bent into another position.
Examples of one type of elongated flexible curler are shown in U.S. Pat. Nos. 1,619,743 and Re. 15,363 showing a wire core within a cylindrical pliable rubber covering encased in a fibrous cover. U.S. Pat. Nos. 2,061,817 and 2,542,601 show flexible hair curlers having a central metal core and a compressible sponge rubber, solid natural or synthetic rubber body molded around the core. More recent prior art is shown in U.K. patent application No. GB 2,111,382 disclosing an elongated curler having a central wire core surrounded by a sleeve and polyethylene foam jacket and having end caps covering the wire ends. U.K. patent application No. GB 2,067,898 shows a curler having a "pipe cleaner" core element extending beyond the curler body in order to enable the ends to be bent back over the body.
None of the aforementioned prior art elongated flexible curlers is identified as being suitable for being heated and for retaining sufficient heat for a sufficient time period to facilitate setting a curl in the hair. Foam rubber curlers are unsuitable for heat retention because they have an open-celled structure with many air pockets which do not retain heat well. While some relatively solid material is required to enhance heat retention, solid rubber curlers are unsuitable because they are relatively hard to the touch, inflexible, and continued exposure to heat would tend to deteriorate the rubber. Natural and synthetic rubber like that used in the curler referred to in U.S. Pat. No. 2,542,601 generally has durometer reading on the order of 30-100 Shore A. This amount of hardness makes the material not sufficiently flexible or elastic for satisfactory curler applications and causes the body material to tend to straighten the wire. Because of the hardness of the body material the core wire must be relatively large to overcome the inflexibility of the rubber. Also, the rubber curler disclosed in U.S. Pat. No. 2,542,601 does not address the issue of flammability of the body material because that curler is not designed to be heated. In a heatable curler nonflammability is important. There is no suggestion in this patent of what material may be used which has all of the desirable characteristics. Furthermore, there is no suggestion in the aforementioned prior art patents as to how to overcome the well-known heat-aging propensity of rubber-based compounds.
U.S. Pat. No. 2,074,816 shows an elongated flexible hair curler having an absorbent casing filled with a material such as calcium oxide which when moistened generates heat. The curler disclosed in this patent is incapable of generating heat in use with dry hair. Additionally, the use of a discrete chemical composition within the curler requires extra effort and expense to insure integrity of the calcium oxide component throughout the life of the curler.
It is an object of this invention to provide an elongated flexible curler capable of being heated and retaining sufficient heat for a sufficient time to facilitate setting a curl in hair wound on the curler.
It is a further object of this invention to provide an elongated flexible curler capable of being heated dry and of retaining heat for a sufficient time in use with either dry or dampened hair to facilitate setting a curl in the hair.
It is yet another object of this invention to provide a heatable elongated flexible curler capable of repeated and continued exposure to high hair curling temperatures without significant deterioration, capable of being bent substantially 180.degree. and retaining such bent position, and having a durometer reading of approximately 30-70 Shore 00.